1. Field of the Invention
The present invention relates to a system and method for preventing spark-on-make in an internal combustion engine, using manifold pressure information.
2. Discussion of the Related Art
A typical automotive ignition system includes a spark plug for each combustion chamber of an engine, at least one ignition coil and at least one device adapted to selectively charge the coil(s) and cause the energy stored in the coil(s) to be discharged through the spark plugs in a timed manner. As a result, a spark is generated and ignition of a fuel-air mixture in each combustion chamber occurs at a specified timing.
When charging of the coil is initiated, however, a transient voltage is created. In some situations, this transient voltage may be high enough to create a spark at the spark plug. This kind of sparking event is commonly referred to as a spark-on-make event or condition because historically it would occur when the breaker points of the ignition system made contact to commence charging of the ignition coil. The term "spark-on-make", as used in this disclosure however, is not limited to situations where conventional breaker points are used. To the contrary, it refers to any situation where initiation of coil or ignition system charging causes a spark at one or more of the spark plugs. This kind of sparking event, however, is undesirable because it is not timed for proper engine operation. It can cause severe damage to engine components.
Recent advances in technology have made it more practical and desirable in some situations to provide a coil-per-cylinder ignition arrangement (i.e., wherein a coil is provided for each cylinder of the engine). While the coil-per-cylinder arrangements provide some benefits and advantages, the spark-on-make condition is more likely to occur in such an arrangement. The spark-on-make conditions or events, as a result, tend to detract from the benefits achieved by providing a coil from each cylinder.
Efforts therefore have been directed at eliminating or reducing the likelihood that a spark-on-make event will occur. While conventional techniques of avoiding the spark-on-make condition can be generally effective, there is significant room for improvement. Many such techniques involve complicated and/or time-consuming manufacturing and/or installation processes, and/or involve customized or otherwise relatively expensive parts. The conventional techniques therefore can be relatively expensive, complicated, and time-consuming.
Examples of the conventional techniques of avoiding a spark-on-make condition include 1) providing a high voltage diode that is used to permit the flow of current in one direction to the spark plug but not in the reverse direction, thereby allowing the coil to be discharged after sufficient charging and at the proper time while preventing application of the transient voltage created during initiation of the charging process, and 2) by reducing the number of turns in the coil.
The first technique is relatively expensive. A high voltage diode can cost several cents per diode, even when purchased as part of a high volume transaction. In automotive manufacturing, where the number of parts and the cumulative cost thereof can escalate, a per-part cost of several cents should be avoided whenever possible. In addition, the use of a high voltage diode is not always compatible with ignition systems that have ion sense capabilities. Typically, the way to provide compatibility of the high voltage diode technique with ignition systems that have ion sense capabilities is to use a positive polarity spark. It is more desirable, however, to not be limited to use of such positive polarity sparks because they have a higher demand voltage (e.g., 10% higher).
The second technique, namely, reducing the number of turns in the secondary winding of the coil disadvantageously tends the increase the overall cost of the coil driving electronics. In some cases, the reduction in number of turns also prevents the coil from satisfying other requirements imposed by the consumer (e.g., an engine or ignition system manufacturer).
There is consequently a need in the art for a less complicated, less expensive, more reliable, and/or more practical system and method for preventing spark-on-make in an internal combustion engine. This need extends to a system and method that is not limited to use on positive spark polarity ignition systems.